Captive Rearing of Peppermint Shrimp (Lysmata wurdemanni):
A Hobbyist's Tale

April Kirkendoll writes in the conclusion of her entertaining book entitled "How to Raise & Train Your Peppermint Shrimp" to, 'tell the world what you discover and don't skimp on the details. Our hobby may depend on it." I sincerely believe these words, and have tried to detail as much of my experiences attempting to raise Peppermint shrimp, so that you might not only observe many of the aspects of shrimp growth, but also may learn and develop novel ways of increasing the post-larval settlement survival rate.

For the first three years of trying to spawn and raise Peppermint shrimp, I could never get the shrimp larvae to survive more than a week or so before they died en masse. Recently, however, I was able to rear them to 5 weeks before they died by feeding copepods, in addition to baby brine shrimp (bbs) and plankton flake food. Here's my hobbyist's tale.

Figure 1. Breeding Adult

The Breeding Adults

Approximately three years ago, I obtained two small Peppermint shrimp, Lysmata wurdemanni, from a local fish store. Since then I've been able to capture roughly half of the larvae (about 50 larvae captured) almost every month. No special attention is given to the adult shrimp. Generally, frozen Mysis and brine shrimp are fed to the tank every day, as well as Tahitian Blend algae paste (see note 1). The adult shrimp will generally eat anything that they can catch and tear apart with their pincers. The shrimp are full sized adults (3") ,and regularly produce free swimming larvae every month (about 100 larvae at each event).

Capturing Larvae

Spawning inevitably occurs late at night, usually around midnight. If the larvae are not removed immediately from a fully stocked reef tank, they stand very little chance of survival because of predation by fish. In my 100 gallon main tank, it is obvious when the larvae are present as the presence of a swarm of shrimp larvae induces the Anthias to go into a plankton feeding frenzy. At that point, I start removing the larvae using a 10 ml plastic syringe with 5 inches of airline host attached to the end. Do not attempt to use a fine mesh net to collect the fragile larvae as the physical contact tends to break appendages. I've observed larvae with missing appendages circle and spin in the grow-out tank and usually die off very soon after. Additionally, I suspect the larvae don't feed as well as those with all appendages. The pumps are all turned off during this process to prevent larvae from going over the overflow, or being distributed around the tank, making it harder to siphon them out. In dark and still water, the larvae naturally group together on the bottom of the tank; which makes it easier to siphon them out. If there is light, the larvae tend to swim toward the light but don't group together well. Even grouped together, it is quite laborious to get them out, and I usually only manage to retrieve about half before tiring. The fish consume the rest.

Initial Grow-Out Tank

Water from the main tank (see Table 1) is transferred to a tiny 1/2 gallon tank containing a single airstone that generates very fine bubbles. Fresh artificial salt water (ASW) is not used because of very high mortality rates (personal observation, Toonen 1999, Strathmann 1987) possibly due to the use of Tris-EDTA or like chelator. One workaround maybe to first run the ASW through granular activated carbon then age under heavy aeration. If the bubbles are too large, the larvae can be damaged from the turbulence. Again, larvae with broken appendages appear to feed less effectively and die sooner than larvae with all appendages. Using an extra small tank for the initial grow-out of the larvae increases the density of newly hatched Artemia, and provides a higher probability that weakly swimming larvae will make contact with the food. Brine shrimp nauplii stocking concentration was roughly 25 per milliliter. A single 9-watt normal output fluorescent light is used to attract both the larvae and brine shrimp to the water surface and away from the airstone. My next version of the rearing tank will be a tank within a tank so I can isolate the larvae from dangerous filtration equipment. The water temperature is kept between 74 and 78 degrees, and no water changes are made for the two weeks of the initial rearing period. Only RO/DI water is added, very slowly, to keep the specific gravity roughly constant at 1.025. The chance of changing water and inadvertently transferring larvae out of the tank is great, and fishing larvae out of water with a plastic 10ml suringe is not an easy task. Larval mortality during the first two weeks is high; I estimate it to be about 50 percent. When the tank bottom begins accumulating detritus, the larvae are transferred to the final rearing tank via a ½ inch inner diameter hose to reduce the chance of larvae becoming trapped in the bottom debris (Castro, 1983).

Larval Rearing Tank

A 10 gallon rearing tank is set up in parallel to the initial grow-out tank using water from the main tank, and any copepods are allowed to grow under 40 watts of normal output fluorescent light. Additionally, copepod growth is encouraged by additions of cryopreserved algae (see note 1). After two weeks, the surviving larvae from the initial grow-out tank are transferred via hose to the rearing tank. Freshly hatched Artemia nauplii are added every other day at a density of about one fifth of what it was in the mini-tank (about 5 per milliliter). However, since the larvae are bigger and are better swimmers with more appendages, finely smashed dried plankton flake is added to the tank as well (Kirkendoll 2001). It is believed that 2-4 week old larvae eat bbs, phytoplankton (Toonen, personal communication 2002; Jaime 2000; Ronquillo 1997), flake food (Kirkendoll 2001) and baby copepods (personal observation; Shishehchian 1999). I've observed 5 week old larvae catch a copepod and eat it, look quite fat afterwards and pigmentation increases afterwards. (See photos 1 & 2 of 4-week old larvae ). Toonen believes (personal communication, 2002) shrimp larvae consume some amount of phytoplankton as part of their diet since shrimp larvae have phyllopodous legs that are typically an adaptation for filter-feeding in marine invertebrate larvae. Toonen has also found Lysmata larvae guts loaded with phytoplankton (Tahitian Isochrysis ) fed hours before. Toonen (pers. comm., 2002) believes only live phytoplankton (e.g. DT's Phytoplankton) should be used since the chemical used to preserve algae paste contributes to sticky surface films and hence a greater chance of trapping larvae.

Figure 2: 4 week old [side view]	Figure 3: 4 week old [top view]

Copepods

I do not know what species of copepod grow abundantly on the glass surfaces of the 10 gallon tank, but I believe them to be harpacticoids (Shimek, personal communication, 2002). The young white copepods (1-2 mm) often dart out into the water column to move from place to place or so make small forays into the water to catch food and are occasionally caught by larvae. The copepods are clearly benthic, spending most of their time in the bottom debris or on the tank sides. The copepods in my tank under 40x magnification have long twin first antennae in the front and very long twin 'tails' in the end (see Figure 4 for an approximate sketch). The females carry sacks of eggs in the tails. These copepods appeared to reproduce rapidly under 40 watts of normal output fluorescent light, daily algae paste and brine shrimp nauplii additions.

Figure 4.

The adults (5 mm) do not exhibit darting behavior and spend most of their time near the bottom. My theory is that the shrimp larvae are able to catch the free-swimming copepod juveniles as they dart out, even though the copepods are much faster swimmers. Occasionally, I would see a shrimp larvae jerk in response to being hit by a young copepod 'missile,' and then retreat. The shrimp larvae intestines contained colored contents (probably flake food), as well as white/gray matter (probably bbs and, I believe, the small copepods). Copepods are believed to be a good larvae food source because copepods are high in EPA/DHA (Toonen, personal communication, 2002) and waxy esters and marine oils (Hoff 1999). Strathmann (1987) reports some epibenthic harpacticoid species are heavily preyed upon by juvenile salmon.

Larval Settlement

According to Riley (1994), Lysmata settlement can occur anywhere between 40 and 65 days, and it is not clear exactly what settlement cue triggers the larvae to become post larvae shrimp. The earliest settlement of 42 days by L. amboinensis was observed at the Waikiki Aquarium in a special 1000 gallon flow-through system using natural seawater, and the larvae were fed heavily on Tetraselmis and rotifers, switching to enriched Artemia at a later time (Toonen, personal communication with Waikiki Aquarium staff, 2002).

Conclusion

I was not able to get larvae past 5 weeks even though the larvae were large (1cm), colorful, and were freely using their pleiopods to swim towards food. I believe my high mortality rate at week 2 then again at week 5 were do to the following four issues that will be the focus of follow-up experiments:

Riley (1994) and Kirkendoll (2001) report maximum survival rates of 22 and 35 percent to post larval settlement, respectively.

…Till the next collection of free-floating Zoea!

Notes

Acknowledgments

The author wishes to thank Dr. Ron Shimek, Eric Borneman and the Saltwater Enthusiasts Association of the Bay Area (SEABay) board members for reading and criticizing the paper. Special thanks to Rob Toonen, larval biologist, for advice and references on phytoplankton, marine invertebrate larvae diets and settlement.

References

Castro, Alceu de, Darryl E. Jory, 1983. Preliminary experiments on the culture of the banded coral shrimp Stenopus hispidus Oliver. Journal of Aquaculture & Aquatic Sciences Volume 3, Number 4.

Hoff, Frank 1999. Plankton Culture Manual Fifth Edition. Florida Aqua Farms. Florida. P106-111.

Jaime, Barbaro; Artiles, Miguel; Fraga, Iliana; Galindo, Jose. Substitution of Chaetoceros muelleri for spray-dried Chlorella vulgaris in feeding protozoae of Litopenaeus schmitti. In: Boletin del Centro de Investigaciones Biologicas Universidad del Zulia Agosto, 2000. 34 (2): 127-142.

Kirkendoll, April 2001. How To Raise & Train Your Peppermint Shrimp. Lysmata Publishing, Miami, Florida. 117 pages.

Riley, Cecilia 1994. Captive Spawning and Rearing of the Peppermint Shrimp (Lysmata wurdemanni). SeaScope Vol 11, Summer 1994. 3 pages.

Ronquillo, Jesse D.; Matias, Jonathan R.; Saisho, Toshio; Yamasaki, Shigehisa. Culture of Tetraselmis tetrathele and its utilization in the hatchery production of different penaeid shrimps in Asia. In: Hydrobiologia Dec. 22, 1997. 358 (0): 237-244.

Shishehchian, F.; Yusoff, F. M.; Omar, H.; Kamarudin, M. S.. Nitrogenous excretion of Penaeus monodon postlarvae fed with different diets. Marine Pollution Bulletin 1999. 39 (1-12): 224-227

Strathmann, M. F., 1987, Reproduction and Development of Marine Invertebrates of the Northern Pacific Coast, University of Washington Press, Seattle and London, 670 pages.

Toonen, Rob 1999. Culturing Shrimp. www.reefs.org 2 pages.

Toonen, Rob 1999. Larvae Settlement Cues. www.reefs.org 3 pages.